26 THE BUTTERFLIES OF NEW ENGLAND. 



situated in tlae middle or posterior part of the dorsum of the fifth abdominal 

 segment, and connected by a slender thread to minute bodies in the poste- 

 rior portion of the under surface of the last segment. The compound 

 organs or testes are placed next to the alimentary canal, those of the oppo- 

 site sides in juxtaposition but with no direct communication. They are 

 more or less elongated, ovate or reniform in shape, bright colored, and 

 quadrilobed, containing each four similar chambers in a row from in front 

 backward ; the anterior extremity of each testis ends in a very short and 

 slender thread. Just behind each testis a delicate pellucid thread arises, 

 which passes posteriorly and a little dowuAvard until opposite the spiracle 

 of the sixth abdominal segment ; here it plunges downward toward it, and 

 passing through the mass of tracheae to those of the seventh segment, 

 sweeps around toward the medio ventral line of the body, and, passing- 

 through an independent muscular bundle scarcely larger than itself, which 

 stretches transversely across the body at this point, enters a minute whitish 

 sac, situated just beneath the termination of the intestine. 



The ovaries of the female are situated in the same place as are the testes 

 in the male, and consist of a pair of long obovate sacs, bluntly rounded at 

 each end, vertically disposed, approximated, but with the lower end curved 

 outward ; they are white, and each consists of a bundle of four similar tubes. 

 The whole structure is completely homologous with the corresponding parts 

 of the male, and as will be seen the future development of the parts in one 

 set is paralleled by that in the other. 



Cellular system. A caterpillar seems made to gormandize ; the muscles 

 are few and either serve to give action to the alimentary canal, to transport 

 the animal to a feeding spot, or to remove the old integument to admit a 

 larger growth and greater capacity for food ; they will not enable it, by 

 rapid movements, to escape an enemy ; those of the head — and there is little 

 but muscle therein — are almost exclusively attached to the jaws ; other 

 organs serve the same pm-pose ; the general cavity of the body is mostly 

 occupied by the alimentary canal and its appendages ; spinning glands fill 

 some of the space, and they are used only to give the insect a foothold 

 when eating or travelling in search of food ; air vessels supply the means of 

 using the food for nourishment ; the nervous system is very slight and most 

 of its ramifications are addressed to the muscles. Yet a considerable por- 

 tion of the material in the cavity shows that this gormandizing has an imme- 

 diate object ; — namely, the storing up of nourishment for future use during 

 the great changes that are to occur during the subsequent quiescent state ; 

 for, completely enveloping the alimentary canal and its appendages and oc- 

 cupying all possible space between this and the muscles, the fatty bodies are 

 really the most conspicuous portions of the interior organism of a caterpillar ; 

 it is upon this that the parasites feed and in consequence of the loss of it 

 that the animal attacked by them finally perishes. 



